- Created by: daisy yemm
- Created on: 21-02-19 15:23
Arrival of an action potential:
- When an action potential from a motor neurone stimulates a muscle cell, it depolarises the sarcolemma.
- Depolarisation spreads down the T-tubules to the sarcoplasmic reticulum. This causes the sarcoplasmic reticulum to release stored calcium ions into the sarcoplasm. This influx of calcium ions into the sarcoplasm triggers muscle contraction.
- Calcium ions bind to a protein attached to tropomyosin, causing the protein to change shape. This pulls the attached tropomyosin out of the actin-myosin binding site on the actin filament.
- This exposes the binding site, which allows the myosin head to bind.
- The bond formed when a myosin head binds to an actin filament is called an actin-myosin bridge.
Movement of the actin filament:
- Calcium ions also activate the enzyme ATP hydrolase which hydrolyses…